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EMC Precompliance Suggestion

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Elscimar

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Hey folks...I'm looking to do some precompliance on conducted emissions, and I was wondering whether or not a USB spectrum analyzer would be suitable. I've got to look between 150kHz and 30MHz, and I just want to check out whether or not my thingy is going to fail that part of the test before I go and spend a lot of money on getting this widget tested. I'm not even going to try to figure out radiated. I just want to be able to screw around with the EMI filter until it works before spending a lot of money on a full EMI test.

Is something like **broken link removed** suitable for this kind of thing?

I just need an analyzer, a preamp, a LISN to plug it into, and the appropriate test setup, right? Do I even need the preamp with that analyzer? It already goes to 10dbm, and if I see anything at even -30, that's a fail.
 
With this signalhound you can not tell if you will pass or not!
If you fail at a real lab....then with the signalhound you can make changes to you product and see how much those changes helped.

If you fail by 4db at 100khz then the signalhound can see how much a fix helped. If you add a capacitor and the 100khz dropped by 6db that is good but that cap may cause 1.4mhz to increase by 7db.

I only trust the singalhound, or any at home measurement, to know if a change helps or hinders and by how much. I never trust this type of testing completely.
 
Right. I know I'm never going to be 100% sure with any kind of measurement I do. They don't even use a spectrum analyzer for this kind of test. I'm just looking to try and get as close as I can before I send it off for testing. Any suggestions on what might get me a bit closer? I'm obviously not looking for a full EMI analyzer, here.
 
I just need an analyzer, a preamp, a LISN to plug it into, and the appropriate test setup, right? Do I even need the preamp with that analyzer? It already goes to 10dbm, and if I see anything at even -30, that's a fail.

No I dont think you need a pre-amplifier, that analyser is sensitive enough as it is.

JimB
 
No I dont think you need a pre-amplifier, that analyser is sensitive enough as it is.

JimB

I see some setups including a transient limiter. Good idea or overkill?

Edit: They're cheap. Might as well stick one in.
 
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Hey folks. It's been a bit, but I've come back to this project. After talking with the Signalhound folks, they say their software isn't up to the task of doing an EMC sweep. However, they have an API, so I'm sure I could throw together something to do that for me.

According to SH, the problem appears to be in image rejection. The SH does it in software, rather than hardware, so I'm not sure how fast I can detect transient events. I guess until I buy and read the spec, I have no way of knowing whether or not I can detect transient events fast enough. (Unless anyone has any experience, here.)
 
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